But this year, university officials joined parents in warning students to consider alternatives because of the drug-related violence that has spiraled out of control. Some travel agencies canceled trips, particularly along the border where most of the bloodshed is concentrated.

In February, the US State Department issued a travel alert, warning of "large firefights" across Mexico and confrontations with cartels resembling "small-unit combat."

"I think it's very important to be aware of what is going on here," says Clara Spas, a senior in business administration at Buffalo State College, who is in Cancún this week with 24 classmates. She says she studied the maps to learn the distance between Cancún and Mexico's most troubled spots before making the trip. She did so mostly to appease her mother – and her school – who urged her to change her plans. "I feel totally safe, even though I feel like I know so much of what is going on here."

There are few places as fabled for a spring break as Cancún, with its azure Caribbean waters and discounts that each year draw students from February through April. The scene this year is no different from years past, with big banners welcoming students, and streets full of flip-flop-clad Americans.

Yet this year many colleges felt obligated to educate students about the underbelly of all the fun. California Polytechnic State University in San Luis Obispo, for example, sent a warning to its student body last Monday, ahead of their spring vacation. "We understand that a number of our students travel to Mexico each year for spring break. This year, increased violence plagues the region," it warned, urging students to leave their full itineraries at home with families in friends.

That warning specified trouble spots, mostly near the border and hundreds of miles from techno parties and beach volleyball. Tour agencies and Mexican tourism officials are trying to reiterate that distinction. "We understand violence is happening, but some [places] are 2,000 miles away, and if students use common sense safety tips, it can be an enjoyable experience," says Patrick Evans, of STA Travel, one of the world's largest student travel agencies. He says they have not had any more cancellations this year than in previous ones.

STA Travel did, however, cancel a bus tour that crossed the border of Texas and headed down the Pacific coast to the resort town of Mazatlán.

Some schools urged students to stay away altogether. "Every student should be aware that Mexico in general has seen a marked increase in violence recently," read a University of Arizona statement released in February. "Due to these circumstances, the University of Arizona Dean of Students Office strongly advises students to avoid travel to Mexico at this time and during Spring Break."

"It's the first time we've recommended to students that they not travel there," says Johnny Cruz, a university spokesperson.

Samantha Fallon, a sophomore at the University of Arizona, was signed up with a travel agency to go camping on an island in the Sea of Cortez. But, she says, that under pressure from the school, the trip was canceled. "I was disappointed. I didn't want the drug war or violence to stop me from having a trip of a lifetime. We were going sea kayaking, cliff jumping, and swimming with dolphins." Instead, she took a road trip through California with some friends. "We saw tons of U of A friends doing the same thing."

While most of the violence has taken place elsewhere, the beach resorts are not entirely isolated from it. In recent years, Acapulco has seen decapitations and gun fights in plain daylight. In Cancún, a retired army general sent to root out corruption in a police force allegedly infiltrated by drug traffickers was recently tortured and shot to death.

Tourism officials are trying to fight back. The Cancún Hotel Association launched a campaign this month, including a YouTube video of American tourists enjoying the area. "We didn't want us telling you Americans how great it is, we wanted you telling each other," says Rodrigo de la Pena, the president of the Cancún Hotel Association.

Tourism grew last year in Mexico, fueling a $13 billion a year industry that is crucial to the economy, but the numbers are down slightly. Cancún expects 22,000 spring breakers this year, down from 26,000 the year before. Occupancy rates are down through mid-March at 79.2 percent this year, compared with 84.6 percent in the same period last year, says Mr. de la Pena. He blames it on the economic situation in the US, not on violence.

Most spring breakers, from Washington State to Wales, say they understand that most violence occurs between drug traffickers. Still, Heidi Frawley, a freshman at Mt. Hood Community College in Oregon, says that she has decided to stay put in the major cities, like Cancún, instead of exploring smaller towns. She adds that the worst experience for her thus far has been police corruption and bribe-seeking.